1. Field of the Invention
The present invention relates to a brake system for use on motor vehicles, and more particularly to a brake system including braking force generating mechanisms mechanically separate from a brake pedal, for applying braking forces to road wheels based on selected different parameters of depression by the driver of the brake pedal.
2. Description of the Relevant Art
Electronic brake systems include braking force generating mechanisms mechanically separate from a brake pedal, for applying braking forces to road wheels of a motor vehicle in response to depression of the brake pedal by the driver. Such electric brake systems have a sensor for detecting the depression by the driver of the brake pedal. In response to a signal from the sensor, electric actuators of the braking force generating mechanisms are energized to apply boosted braking forces to the road wheels.
One known motor vehicle brake apparatus is disclosed in Japanese Laid-Open Patent Publication No. 60-206766 (corresponding to U.S. Pat. No. 4,658,939), for example. The disclosed motor vehicle brake apparatus tends to make the driver feel awkward because it controls the braking forces based on either depressing forces applied to the brake pedal by the driver or a stroke by which the brake pedal is depressed by the driver. More specifically, the ordinary driver of motor vehicles with usual mechanical brake systems adjusts the braking forces by varying the stroke of depression of the brake pedal when the motor vehicle is to be braked with relatively small deceleration in normal traffic conditions, and also adjusts the braking forces by varying the depressing forces applied to the brake pedal when the motor vehicle is to be braked with relatively large deceleration in case of emergency. Since the driver adjusts the braking forces in these different modes depending on the traffic situation, the driver is unable to get natural responses that match the driver's feel if the braking forces are controlled based on either the depressing forces on the brake pedal or the depressing stroke of the brake pedal.